Inductance device



Nov. 16 1926. fl

L. R. GUILBAUD INDUCTANCE DEVICE Filed July l, 1924 Patented Nov. 16,1926..y

UNITEDsTATEsPATENT oFFlcE.

LUCIEN GUILBAUD, NEW YORK, N. Y., ASSIGNOR TO WESTERN ELECTRIC COM-PANY, INCORPORATED, OF NEW YORK; N. Y., A CORPORATION OF YORK.

' INDUCTANCE nnvron.

Application med my 1,

This invention relates to inductance devices known in the art as retardcoils, transformers and the like, and particularly to shell-typemagnetic cores for such'devices.

An object of the invention in general is to provide a convenient andsimple method for controlling the magnetic stability and inductance ofinductance devices such as retard coils, transformers and the like, andmore specically to provide means for producing commercial shell-typelaminated cores for such devices in which an increased range of magneticstability and reluctance may be obtained.

A further object is to provide a shell-type laminated core having areluctance intermediate between that obtainable when there is asubstantially closed magnetic path in each of the limbs of the core, andwhen an air-gap is provided in each of the limbs of the core.

A feature of the invention comprises a stacking of the laminationsections to provide a continuous airlgap in certain of the branches of'a multi-layer core and no air-4 gaps in others of the branches.

In inductance devicesof the kind referred to above when used forcarrying superimposed direct current, it is necessary that the magneticpath be provided with an air-gap or air-gaps to prevent an appreciabledecrease in the inductance of the windings with increasing values ofdirect current. Air-gaps are readily provided in laminated cores made upof lamination sections by stacking the sections so that the jointsbetween sections of successive layers coincide. The value of inductanceand the degree of magnetic stability required for any'particular purposemay be obtained by controlling these air-gaps. This control becomesespecially diicult in the case of core materials of high permeability,such as permalloy, for example, which is especially sensitive to changesin' magnetiang forces. y

In accordance with the invention, it has been found that by variousarrangements of the lamination sections, different intermediate corereluctances can be had between the no-gap condition and the conditionwhere air-gaps are present as heretofore obtained by stacking of thelamination sections. It has been found, for example,

that inthe three-limb type of closed core 1924. serialliio. wam.v

in addition to a gap in each of the three limbs, either` a gap in thecentral limb alone, or a gap in each of the outer two limbs only, may beobtained depending on the manner of stacking, and for each arrangement adifferent core characteristic is ob tainedi The invention thus providesa simple and effective method of obtaining graded core characteristicsin cores of the same dimensions made up of identically` the samelaminations. Y

The invention is hereinafter described in connection with a transformerhaving a substantially shell-type magnetic core com: posed of aplurality of laminations. Each lamination consists of a plurality ofseparate pieces of core material, the points where the pieces of eachlayer come in contact with each other forming small air-gaps. In theembodiment to be described, the pieces forming each layer arespecifically an F shaped and an L shaped strip, which, when placedtogether, form a two mesh magnetic core of the shell-type.

For a better understanding of the invention, reference is made to theaccompanying drawings in which Fig. 1 represents a transformer in whichthe laminations of the core are arranged in such a way-as to obtainmaximum magnetic stability in the core; Fig. Qillustrates thesam'enumber of laminations arranged in such a manner as to give thetransformer windings a maximum inductance; Fig. 3 shows the same numberof laminations arranged so as to obtain a magnetic'stability superior tothat obtained in the arrangement of Fig. 2 and an inductance larger thanthat obtained ,in the arrangement of Fig. 1; Fig. 4 shows an arrangementof the laminations to give the transformer windings aninductance and amagnetic stability intermediate between that obtainable in thearrangements shown in Figs. l and 2. In eaclnfofr` the drawings theupper two laminations are shown de-v tached from the-rest ofthelaminations to l illustrate more'clearly-the arrangement of the F and Lparts. n Throughoutl .the several drawings, .likeparts bear.- like'.`reference characters. u

Referring in "detail to 'the -.drawings,. Fig. 1 shows a transformer.-having a. magnetic corel composed ."ofja plurality of Flshaped pieces 2'and a plurality of L-'shaped jpieces 3; Mounted on a' portion`4 oftheF-'s'hape'd lilo pieces is a spool comprisingv a primary winding and asecondary winding 6. It is obvious that if the laminations are arrangedas in Fig. 1 with all the L-shaped pieces on one side and all theF-shaped pieces on the other side of the core, a complete air gap 7, 8,9 is obtained in each of the three limbs of the core and the reluctanceand magnetic stability of the core for a given width of air-gap are thena maxminm.

If the F and L-shaped pieces 2 and 3, respectively, of the laminationsare staggered one at a time, as shown in Fig. 2, each side of the corecomprising an equal number of F and L-shaped pieces, then asubstantially closed magnetic path is formed in each of the three limbsof the core, since at the airgaps the magnetic lux can pass to theadjoining lamination which has no corresponding air gap, the reluctanceof the air-gaps between the faces of the adjoining laminations beingreduced to a minimum. Vith this arrangement, a minimum reluctance of themagnetic circuit and', therefore, a maximum inductance of thetransformer windings is obtainable.

In the arrangement ofthe laminations shown in Fig. 3, the F and L-shapedpieces of the laminations are staggered so that complete air-gaps l0 areformed in the outer limbs of the core. However, in the central branch ofthe core a substantially-closed magnetic circuit is formed, since at theairgaps of each lamination the magnetic flux can pass to the adjoining`lamination which has no corresponding air-gap, the reluctance oftheair-gaps between the faces of the adjoining laminations being a minimum.With such an arrangement, the reluctance and lmagnetic stability of themagnetic circuit of the core will be less than that obtained in thearrangement of Fig, 4, which forms a complete air gap in the middle limbof the core and a substantially closed magnetic circuit in the outerlimbs, and more than that obtained in the arrangement of Fig. 2. whichforms a substantially closed magnetic circuit in all of the limbs of thecore, for the reason that as has been found experimentally, complete airgaps in the outer limbs of the core have relatively 'lesseffect inincreasing the reluctance of the magnetic circuit than one air gap ofthe same Width in the central limb of the core. A probableexpl'anationof this is the following. In the arrangement of Fig. 3, there are twomagnetic paths in parallel, and

therefore, any variation in the reluctance of one of them, due toirregular-shearing of the shaped parts of thelaminations` had been cutso that its middle limb was slightly longer than its outer' limb, therewould be an increased air-gap i-ngone of the outer limbs of the core,and each of the L parts of the laminations would be able to move aboutthe extremities of those middle limbs thus producing in one magneticpath an increased reluctance, and at the same time an e'diuivalcntdecreased reluctance in the other magnetic path. The two effects Wouldresultin a constant reluctance for the whole core. However, it isapparent that an air-gap in the central limb of the core will affectboth magnetic paths in the core, and, therefore, any change in the Widthof this air-gap due to irregular shearing of the lamination sections,imperfect contact of these-sections, or other causes will have anincreased eii'ect on the total reluctance of the core.

Fig. 4 shows an arrangement with the F and L-shap'ed parts of thelaminations staggered so as to form a complete air-gap 1l in the centrallimb of the core and a substantially closed magnetic path in each of theouter limbs of the core. The reluctance of the magnetic circuit of thecore in such an arrangement will be less than that obtained in thearrangement of Fig. 1 and more than that of the arrangement of Fig. 2,and, therefore, the inductance and magnetic stability given to thetransformer windings will be intermediate between that obtainable withthe arrangements shown Ain those figures.`

The four different ways of assembling the core described above will befound to cover a range of reluctance and magnetic stability suiiicientfor many practical purposes withvantage in cores of high permeabilitymagnetic material, as in permalloy cores, for instance, in which thewidth of the air gap sufficient to produce the desired magneticvstability has 'been found to be of the order of 0.002 or 0.003 of aninch. From the foregoing, it is seen that the F and L shaped lpieces ofthe laminations Imay be arranved in a shell-type'eore so as-.toobtaine't er \one air' gap in each of the outer limbs of the core and a,substantially closed magnetic path in the central limb o thefcore, orone air gap in the; central limb and substantially closed magnetic pathsin the outer limbs of the core, in `addition to the arrangements show nin Figs. l and 2 which are commonlyv used; and that with each differentarrange ment, a' different characteristic is obtained for the core, withthe each case. n

lAlthough for convenience-of description, the invention has been`described andv illusf trated in connection with transformers,`it issame core pieces in;

' applicable as well to other t es of induct- `laminations consistingofvv a v the specification and claims is vmeant sem sitiveness tovariations in magnetizing forces. While no windings have beenillustrated in connection with the laminated cores of Figs. 2, 3 and 4,it is to be understood that either the transformer windings of Fig. 7 orany other suitable type of inductive winding may be used therewith.

What is claimedV is:

l. In an inductance device having a `Winding, a plural-branch magneticcore therefor made of laminations each. composed of sections arrangeableto control the inductance and magnetic" stability by stacking thelamination sections to provide at least one branch" of the core Withoutacomplet'e air-gap and at least one other branch of the core with acomplete `air-gap;w v

2. In an inductance device having av Winding, a core therefor comprisinga' central limb andv outer. limbs,- the` core` also .com-4 prising aplurality of layers of magnetic v ing, a core therefor having a centrallimb and outer' limbs, said core comprising also a material, each layerconsisting of a plurality of separate strips, the strips which make upthe core being arranged in such a manner as to form' a complete air-gapin eachl of said outer limbs of said core and a substantially closedmagnetic path in .said central limb of said core.

3. In an inductance device, a Winding and core therefor, the corecomprising a central limb and outer limbs. the `core also con` prisinga' plurality ofy layers of magnetic material, each layer consisting ofla separate F-shaped strip and a separate L-sh'aped strip, the F-shapedand the L-sha'ped strips which -stantially closed magnetic vtral limb.

yhavin malie up the core being so arranged asto form an air-gap in saidcentral limb and a substantially closed magnetic.y path in said outerlimbs of said, core.

4. A core for an inductance device, the core comprising a central limband outer limbs,- t'he core also comprising a plurality of layers of4magnetic material, each layer comprising a separate F-shaped part and aseparate L-shaped part, the F-shaped parts and the L-shaped parts whichmake up the core being so arranged as to form a complete air-gap in eachofsai'd outer limbs and a subpath -`in said cen- 5. A core for aninductance .device the core having a central limb and outer limbs, thecore comprising also a plurality of layers of magnetic material, saidmagnetic material a permeability high in comparison with Silicon steelcoreY material, each of said layers comprising a separate E-s'hapedpiece anda separateL-shaped piece, the F-shaped pieces and L-shapedpieces'which make up the core being so arranged as toV 'form -a'complete air-ga in each of! said outer limbs of said core an asubstantially closed mag. netic path in said central limb of said core.L

6. In an inductance device having a-wind-ly f plurality of layers ofpermal oy magnetic material, each of said layers consisting of anyFshaped and an L-shapedl piece, the

'F-shaped and -L-shaped pieces which make up the core being sopositioned as to form a complete airlgap in each of said outer limbs nslof said core` and a` .path of negligible re- LUCIEN R. GUILBAUD.

